2-Methyl-2,4-pentanediol (MPD) is an organic compound with the formula (CH3)2C(OH)CH2CH(OH)CH3. This colourless liquid is a chiraldiol. It is produced industrially from diacetone alcoholbyhydrogenation.[4] Total European and USA production was 15000 tonnes in 2000.[5]
2-Methyl-2,4-pentanediol exists as two enantiomers, (4R)-(−) and (4S)-(+). In the Protein Data Bank, the 3-letter code "MPD" refers to the (S)-(−) enantiomer, while "MRD" is used to refer to the (R)-(+) version. Commercial products labeled "MPD" are usually the racemate,[6] also sold as and referred to as "hexylene glycol".[7][8]
2-Methyl-2,4-pentanediol exhibits both surfactant and emulsion-stabilizing properties. Its relatively high viscosity and low volatility are advantageous in coatings, cleansers, cosmetics, solvents, lubricants, and hydraulic fluids.[9] Although it is an irritant at higher concentrations, it is sometimes used in skin care, hair care, soap, and eye cosmetic products at concentrations ranging from 0.1% - 25%.[10][11]
It is biodegradable and unlikely to accumulate in the environment.[12]
In the laboratory it is a common precipitant and cryoprotectantinproteincrystallography.[13] Since hexylene glycol is compatible with polar and nonpolar molecules, it competes with the solvent in a crystallography experiment causing the protein to precipitate.[14] Hexylene glycol is so effective in protein crystallography because its amphiphilic nature and small, flexible structure allows it to bind to many different locations on a protein secondary structure including alpha helices and beta sheets.[15] When hexylene glycol binds to these different locations, water is removed and the protein crystals anneal, which prevents ice formation during cryocrystallography techniques.[16] Incorporation of hexylene glycol into solution has been known to improve the resolution of X-ray diffraction making protein structures easily identifiable.[17] Additionally hexylene glycol is not a strong denaturing agent and thus does not significantly alter the structure of a protein during the crystallography procedure.[15]
Hexylene glycol is also used as a lubricant for polishing specimens in metallography.[18]
^Stylianos Sifniades, Alan B. Levy, "Acetone" in Ullmann’s Encyclopedia of Industrial Chemistry, Wiley-VCH, Weinheim, 2005. doi:10.1002/14356007.a01_079.pub3
^Dumetz, A. (2009). "Comparative Effects of Salt, Organic and Polymer Precipitants on Protein Phase Behavior and Implications for Vapor Diffusion". J. Cryst. Growth. 9 (2): 682–691. doi:10.1021/cg700956b.
^Viatcheslav, Berejnov (2006). "Thornea Effects of cryoprotectant concentration and cooling rate on vitrification of aqueous solutions". J. Appl. Crystallogr.
^Vera, L (2006). "Strategies for Protein Crystallography". Cryst. Growth Des.
^"GreenLube". Allied High Tech. Retrieved 2023-09-23. GreenLube is a medium viscosity hexylene glycol based lubricant used for general metallographic preparation
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